Chev 4.3 Engine Slight Miss Timing Issue

There was some discussion a while back on here about a slight miss in a Chevrolet 4.3 engine possibly caused by moisture or condensation from an A/C line. There was also some very good comments from someone about setting the timing using an older distributor hold down.

I searched and could not find the old thread. I would really appreciate the previous poster with the great information sharing it again. Thanks

I had a 96 blazer with a 4.3 and it would crossfire to dry heater hoses you could see it in the dark. We had to put in a heater core and was told that is what caused it.

What year model? And what vehicle?

2000 Astro Van

(quoted from post at 12:13:44 07/22/19) There was some discussion a while back on here about a slight miss in a Chevrolet 4.3 engine possibly caused by moisture or condensation from an A/C line. There was also some very good comments from someone about setting the timing using an older distributor hold down.

I searched and could not find the old thread. I would really appreciate the previous poster with the great information sharing it again. Thanks

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I believe it was posted on "Tales" by George from Terre Haute. After so many days, "Tales" runs off the end of the spreader (so to speak) and the oldest posts are lost.

There's lots of theories about how the innards of those distributor caps corrode so badly, and GM has issued some service bulletins over the years regarding the screened vents in the distributor base, etc..

As I understand it, it MAY help to get the AC lines away from near the cap and /or insulate them 'cause the cooling effect on the cap MAY cause more condensation inside.

Cam sensor (which is in the distributor) offset is not adjustable after a certain year because of the pinned distributor holddown.

Theory is that is you defeat that and tweak the distributor position to get the cam sensor offset as close to "0" as possible, (need a scan tool to check this)the rotor tip will be closer to each individual high tension terminal when spark occurs, making for a shorter distance for the spank to jump between the rotor tip and high tension terminal, a shorter spark inside the cap = less ionized air and less corrosive ozone which (along with moisture) tears up the aluminum high-tension posts inside the cap.

Clear as mud, I hope?

Also, be aware that tweaking the distributor a little one way or the other won't affect spark timing, that's determined by the CRANKSHAFT position sensor and where the 'puter is "looking" in the "advance table" for a given set of operating conditions.

(That seems hard to swallow for us old guys used to tweaking the distributor position to set spark timing!)

As I previously wrote, the idea is to have the high tension terminals correspond as closely as possible to the tip of the rotor when another part of the system "fires" the coil.